TSO Products DoubleGroove 20mm Tall Rail Dogs We've reinvented the 20mm bench dog with some TSO-firsts that improve ease-of-use and comfort. Use these dogs to position your workpiece for square or angular cuts, use them to attach our PTR-18 or MTR-18 Precision Triangles to your worktop, or use them in conjunction with Dog Rail Clips to secure your guide rail to your worktop.